1. Field of the Invention
The present invention relates to overbased sulfurized alkaline earth metal phenates and a process for preparing same. More particularly, the present invention relates to overbased sulfurized alkaline earth metal phenates which are oil soluble, excellent in detergency dispersancy and have high base value, and to an effective process for production of said overbased sulfurized alkaline earth metal phenates under conditions providing less sludge and less raw material recovery. Further, the present invention relates to lubricating oil additives containing said overbased sulfurized alkaline earth metal phenates as main ingredients and lubricating oil compositions which comprises said lubricating oil additives and lubricating oils.
2. Description of Related Art
In general, basic phenate type detergents are used in lubricating oil for internal combustion engine, and used as lubricating oil additives to neutralize acids such as oxyacid and sulfuric acid; to disperse sludge, lacquer, carbon and the like, and to prevent corrosion abrasion and sticking of piston packing rings.
However, the currently used basic phenate type detergents have problems, for example, they are less soluble in lubricating oil, and produce deposits in the engine, preventing normal operation.
Accordingly, techniques to produce basic phenate type detergents by various methods have been developed to solve such problems. For example, a process for production of calcium phenate using .alpha.-olefin as a raw material is described in Example 8 in Japanese Patent Publication No. 28878/1985. However, the product obtained by this process has low base value and poor dispersancy.
Calcium phenates with high base value are also known as improvements over said calcium phenate. But these have insufficient heat stability and detergency dispersancy.
Further, J. H. Walker, N. P. Seals, W. T. Stewart et al. report that they obtained sulfurized phenates by reacting a mixture of alkyl phenol, alkaline earth metal compound, ethylene glycol and sulfur in U.S. Pat. No. 2,680,096. But these phenates have poor stability and poor oil-solubility as lubricating oil additives. In U.S. Pat. No. 3,036,971, F. P. Otto reports he has upgraded the products by adding a CO.sub.2 treatment step to the process of J. H. Walker. This process, however, can not provide products with sufficient base value.
W. J. Fox, J. Pennint et al. have succeeded in adding 1.5 times calcium to those done by F. P. Otto et al. (see Japanese Patent No. 474042). This process, however, requires that dihydric alcohol and calcium hydroxide be added to the reaction mixture and the reaction be repeated again. W. W. Hannemann has succeeded in compounding more alkaline earth metal per alkyl phenol compared with the product obtained by the process of F. P. Otto et al. (see Japanese Patent No. 437377). However, this process requires to add a metal salt of sulfonic acid and higher alcohol as raw materials in the process of F. P. Otto et al. In Japanese Patent Nos. 533078, 533079, 613542 and 613543, Sakai and Hori et al. disclose a process for production of basic phenate containing more excessive metal compared with those obtained by the conventional processes. However, this process also requires to use higher alcohols.
In Japanese Patent Publication No. 28878/1985, Hori, Hayashida et al. describe a process for production of basic phenates saving raw materials by using alkaline earth metal compounds with a lower stoichiometric amount of alkyl phenol. However, this process have several problems. For example, a large excess amount of starting alkyl phenol must be used to obtain the products and a large amount of alkyl phenol must be recovered.